The invention generally concerns a locking device and an apparatus for tightening a safety belt in a vehicle such as a motor vehicle, for eliminating slack in the safety belt when fitted to the body of an occupant of the vehicle, which apparatus uses the locking device.
Such a locking device can be used for securing at least two components which are movable relative to each other under the effect of a force acting thereon, in a locked position which corresponds to a rest position. Such a locking device is provided with a release mechanism by which the two components can be released from the locked position thereof. Typically such a locking device may be used in an apparatus for tightening a safety belt in a vehicle. More specifically, such an apparatus is designed to cause a safety belt to be applied in a taut condition around the body of the occupant of a vehicle in response to an extreme variation in speed and in particular in response to an impact loading or crash loading which is caused by the vehicle being involved in an accident. The apparatus thus removes from the belt the slack or looseness which is usually to be found in the belt under normal driving conditions where there is no need for the belt to be tightly fitted to the occupant of the vehicle. It will be appreciated however that the slack in the belt can give rise to the danger that, in the event of an accident involving for example a front impact, the occupant of the vehicle may be thrown forwardly to an excessive degree. The belt tightening apparatus is intended to prevent that from happening.
An arrangement of that kind generally comprises a sensor for detecting the extreme variation in speed of the vehicle in the event of an accident, and a locking device with which a locked force storage means is released to produce the belt tightening movement component which is effective to remove slack from the belt. It will be seen therefore that there is a transmission means between the sensor and the locking device. The force storage means is initially in a stressed and locked condition, and it is released from that condition in response to a suitable actuating message transmitted thereto from the sensor, by way of the transmission path. Electrical and/or magnetic transmission means and mechanical transmission means may be used to provide that transmission path. That however means that a certain time inevitably elapses between the response of the sensor, and release of the force storage means. Furthermore additional components are required in order to put the force storage means into the unlocked condition so that the belt tightening movement can be appropriately transmitted to the safety belt to remove slack therefrom.